


Serpensortia

by FantasticNumberNine



Series: John Watson and the Chamber of Secrets [7]
Category: Harry Potter - J. K. Rowling, Sherlock (TV)
Genre: ...that's not really a spoiler..., ...with lockhart..., AU, And a snake, Crossover, Dueling club, Gen, Holmes Brothers, People get petrified, Polyjuice Potion, Potterlock, There's some yelling..., boys in girls toilets, johns a parselmouth
Language: English
Status: Completed
Published: 2014-09-03
Updated: 2014-09-03
Packaged: 2018-02-16 01:25:43
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,751
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2250687
Author URL: https://archiveofourown.org/users/FantasticNumberNine/pseuds/FantasticNumberNine
Summary: <blockquote class="userstuff">
              <p>The boys rush to start the Polyjuice Potion in wake of a new attack, and even joining the new Dueling Club won't protect more students (and ghosts) from falling prey to petrification...</p>
            </blockquote>





	Serpensortia

**Author's Note:**

> *disclaimer*
> 
> I did mention having Sherlock interact with Mycroft. Of course, it went well...

John's first thought as he was released from the Hospital Wing was to find Greg and Mycroft--he needed to tell them about Dobby, and Colin Creevey--but they weren't in Gryffindor Tower, nor had Mycroft managed to drag Greg into the library on a Sunday.

He did find Percy, Greg's older brother and Gryffindor Prefect. 

"I do hope Greg's not in another _girl's toilet_."

John's laugh was a bit forced, but he made his way to Moaning Myrtle's bathroom quickly once Percy was out of sight.

His friends were locked in a cubicle, a cauldron perched on the seat of the toilet, a fire crackling beneath it. He raised both eyebrows.

"Well, we reckoned this would be the safest place to brew the Polyjuice Potion; seeing as no one ever comes in here," Greg shrugged in the tight space, a sheepish grin on his face.

"We overheard Professor McGonagall speaking with Professor Flitwick this morning, about Colin Creevey's being petrified (I assume you know, having spent the night in the Hospital Wing), and decided to proceed with the potion immediately--"

"--Otherwise we'd have met you earlier, but, the sooner we start, the sooner we can interrogate Moriarty and get his confession. He probably took his anger out on poor Creevey because of the match-- _amazing_ catch yesterday, right under his smug, creepy face, the little--"

"Gregory, if I have to listen to you describe _again_ , in vivid detail, all of Moriarty's faults, I will empty this cauldron down your robes, without letting it cool properly first," said Mycroft, calmly tearing bundles of knotgrass and tossing them into the cauldron.

John spoke up before Greg could retort.

"Dobby came to visit me in the middle of the night."

Greg and Mycroft looked up, bewildered. 

"He said the Chamber of Secrets had been opened before, fifty years ago. That's why he didn't want me coming back this year; he's the reason the gateway wouldn't let us through the platform, and it was _his_ damn bludger that tried to kill me during the match yesterday."

Greg frowned, "Why'd he try to kill you if he wants you safe?"

"He thought if I was injured badly enough, they'd send me back to the Dursley's."

Mycroft clenched his jaw, but said nothing as he prodded leeches to the bottom of the cauldron.

"Mental," Greg shook his head. "But that settles it, doesn't it? Mr. Moriarty must've opened the Chamber when he was at school, and now he's told dear old Jim how to do it. Wish Dobby had told you what kind of monster it was, I'd like to know how nobody's noticed the thing sneaking around."

Mycroft looked as though he was considering something rather hard as he watched Greg pour dead lacewings into the potion.

"You know, John," Greg went on, "If Dobby doesn't stop trying to save your life, he'll probably end up killing you."

~~~~~~~

There was a great deal of shouting down in the common room when John came down from the second year bathrooms.

"I don't need your _protection_ , Mycroft!"

Greg was pretending to work on an essay beside them, but beckoned John closer when he saw him.

"What's going on?"

"Mycroft caught the twins trying to, eh, 'cheer up' Sherlock near the second floor--which they'll probably take as encouragement, even if they'll probably be spending the night in the hospital wing." 

Greg seemed more worried about the ongoing dispute between Mycroft and Sherlock than the prospect of his own brothers being hospitalized by Mycroft.

"You are not staying, Sherlock! Why are you still arguing? Mummy's already written to say she would be at the station with father to collect you--they're even bringing Redbeard--"

"Why do you get to stay here? It's unfair!"

"I'm spending Christmas with John--and Gregory--why is that so difficult for you to understand?"

"Because you aren't spending it with me!"

The entire common room was holding it's breath. John wanted to say something--anything--to break the tension, but he didn't _know_ Sherlock, he had no idea how to calm the strange curiosity that was Mycroft's elusive younger brother.

"Sherlock, I have spent _countless_ Christmases with you, at home, entertaining your every whim. Would you truly begrudge me for spending _one_ Christmas with someone who doesn't pretend to hate the holiday?"

"I don't hate Christmas! I hate you!"

Mycroft watched Sherlock run up to his dormitory, looking momentarily grieved before turning a murderous glare on his housemates who quickly returned to their previous activities with varying degrees of tact. Mycroft slumped down into the sofa between John and Greg, not even arguing when Greg slung an arm around his shoulders.

~~~~~~~

John was fairly certain he would be on a morning train back to the Dursley's, but for all the difficulty he had in falling asleep after his stunt in potions, no summons came for him over the incident, and a week later Greg had tired of John's worries.

"You threw the damn thing in _Molly's_ cauldron; our great git may be a bastard for suggesting _Molly_ , but he was right in saying Snape would never suspect a Gryffindor would sabotage one of their own," Greg was saying as they got dressed. "You're actually a bit scary, you know that, Myc?"

Mycroft rolled his eyes as he adjusted the knot in his tie--which always had the gall to look more posh than was reasonable for a second year Gryffindor.

"If you actually found me the least bit fearsome, you'd have stopped calling me 'Myc' the first time I hexed you for it."

There was a small crowd gathered around the notice board by the Great Hall, inviting the students to participate in a dueling club, and the boys were no less excited than their peers about attending. The school was abuzz, rumors and speculations on who would be teaching flying about with as much fervor as the wild gossip over Slytherin's heir--though thankfully with less mention of John.

"So long as it's not _Lockhart_ , they could have Fluffy teach it and I'd be happy," Greg said quietly to John as they gathered in the Great Hall with the rest of their eager peers. 

Mycroft threw Greg a dirty look, having heard the comment despite its volume. Greg smiled innocently until Lockhart's booming voice echoed through the Hall. John couldn't help but share in Greg's horrified groan.

"Gather round, gather round! Can everyone see me? Can you all hear me? Excellent!"

"D'you think if we snuck out now, anyone would stop us?" John whispered.

"Mate, half the crowd here would probably follow you out, Heir of Slytherin or not," Greg muttered back.

Mycroft elbowed both of them, "Hush!"

"--Train you all up in case you ever need to defend yourselves as I myself have done on countless occasions--for full details, see my published works."

John and Greg rolled their eyes. Then Snape joined Lockhart on the stage, Lockhart announcing loudly that they would be giving a demonstration--trading looks, John and Greg planted their feet, arms crossing as eager grins spread across their faces.

"This is going to be brilliant--"

"Snape is going to _murder_ him--"

John wasn't sure why Lockhart was still smiling, if Snape ever leveled a look like that at him, his Gryffindor bravery be damned: he'd run the other way.

"On the count of three, we will cast our first spells. Neither of us will be aiming to kill, of course."

"I wouldn't bet on that," John muttered. Greg snorted.

When the Slytherins cheered Snape sending Lockhart arse over teakettle, John and Greg found themselves hard pressed not to join in.

"Do you think he's alright?" Mycroft squeaked.

"Who cares!" John and Greg said together, doing a poor job of not laughing.

Everything was a lot less humorous when John found himself facing off against Moriarty in front of the entire Dueling Club. He didn't think much of his chances; Snape was murmuring something to Moriarty, all he had was a wand-dropping Lockhart.

Moriarty grinned, "Scared?"

"You wish," John glared.

Lockhart patted John's back, "No need to worry John, just do what I did!"

"What, drop my wand?"

Lockhart hadn't heard.

" _Serpensortia!_ "

A great black snake exploded out of Moriarty's wand, hissing angrily as it hit the ground and lifting it's head to strike. The crowd that had been pressing up against the platform backed away quickly, with several students screaming. 

John stood frozen, clueless how to react, until Lockhart sent the serpent flying and it landed, spitting, slithering madly toward Henry Knight. Then John was leaping forward, though he didn't know why, yelling thoughtlessly at the snake as he did:

"Don't hurt him!"

Miraculously, or rather, inexplicably, the snake obeyed, turning great black eyes to John as it curled docilely where it lay.

The muttering in the hall was suddenly too loud as Greg pulled John away, leading him quickly out and away from the Great Hall, Mycroft beside them.

"Merlin, John! When were you going to tell us you're a bloody Parselmouth?" Greg exclaimed at last, slamming the door to the second floor girls toilets behind them.

"I--what?"

"He didn't know--and how could he? He was raised by muggles--"

" _You_ know--"

"Of course _I_ know, _I_ wasn't raised by--"

"When you're done, maybe one of you could try explaining _what the hell is going on_?"

Greg stared at John gravely, "You can talk to snakes."

John blinked.

"Well, yes. I set a boa constrictor on my cousin two years ago--he was born in the zoo and wanted to see Brazil... What?"

Mycroft and Greg were both wide eyed and staring.

"If you call me _the slow one_ , ever again, I swear Myc, I am reminding you of this moment."

John sought out Henry Knight afterwards, to explain, but everywhere he looked, he could not find him. Finding out that he was hiding in the Hufflepuff common room, terrified John was going to petrify him next, made John's blood boil. It was truly ridiculous, and just the sort of thing that he was beginning to suspect would happen to him for the rest of his life. He was fuming as he stormed out of the library, and not paying the slightest bit of attention to his surroundings as he muttered angrily.

As he tripped over something, nearly falling on his face, he growled.

"What--"

He had fallen over the petrified form of Henry Knight, Nearly Headless Nick floating just as frozen beside him.

**Author's Note:**

> Sherlock is painful for me to write, can you tell? I can. But after CoS I won't have to worry about him much until OotP, so there is that. He'll be older then. I like writing the trio! Greg and Mycroft bickering is great fun. Not sure how John stands them, really...


End file.
